1. Technical Field
The present invention relates generally to suspension systems for rail-supported tools and more particularly to a suspension system having reduced weight and frictional characteristics to reduce the effort with which a tool is moved along a set of rails.
2. Discussion
In assembly plants for automotive vehicles, it is common practice to hang a pair of rails or runways above or parallel to an assembly line. The pair of rails are then used to hang various tools, such as hoists, fastening equipment, fixtures, gages and articulating arms which are used in the assembly process. Often times, these tools can be hung from a single rail with a single trolley set where the weight of the tool is relatively small. The trolley set includes a plurality of rollers which permit the tool to be moved in a direction parallel the rail.
If the tool is configured in a manner where it is not desirable to hang it from a single rail, as when the weight of the tool prevents it from being safely hung from a single rail, a suspension system having a support structure is typically employed. Generally, the support structures used in these suspension systems are H-shaped with four trolley assemblies, one trolley assembly being coupled to each leg of the support structure. While such suspension systems have proven themselves to be robust, several drawbacks have been noted.
One drawback with the suspension systems having an H-shaped support structure concerns their weight and the ease with which they can be pushed along the rails to move the tool to a desired location. As these suspension systems typically weigh up to several hundred pounds, it is frequently difficult for assembly technicians to move the tool and suspension system along the rails to a desired position.
This situation may be alleviated through the incorporation of an electric or pneumatic tractor system to the suspension system wherein the tractor system includes a drive motor to push the suspension system along the rails. Such tractor systems, however, are costly to purchase and maintain and are often more cumbersome to operate than suspension systems that must be manually positioned.